1. Field of the Invention
This invention relates to electrical controls and in particular to cam operated switch means.
2. Description of the Prior Art
In U.S. Pat. No. 3,648,478, of applicant, which patent is owned by the assignee hereof, a defrost control for a refrigeration apparatus is shown to include a double throw switch controlling the operation of a timer motor alternatively connected in parallel with and in series with the compressor motor of the apparatus. In each of the thrown positions of the double throw switch, the timer motor is energized so as to continue the timing operation. However, should the switch stop in a dead break position where the moving contact is not in engagement with either of the fixed contacts of the double throw arrangement, the timer motor will be de-energized and further operation of the control prevented. As the throwing of the switch is effected by cam means driven by the timer motor, gradual camming of the switch from one condition to the other may, at times, result in opening of one closed circuit without closing the other, thereby causing such discontinuation of the operation of the control. The present invention is directed to remedying such a problem.
Another adjustable switch for timers is shown in U.S. Pat. No. 2,578,824 of David Morrison. The Morrison switch means provides a snap action in both directions of operation of the switch by utilizing two movable members for controlling the cam follower. The spring bias of the switch is utilized to obtain a rapid opening thereof and a separate spring biasing the movable members is utilized to obtain a rapid closing thereof.
David Morrison, in a subsequent U.S. Pat. No. 2,617,900, shows a defrosting timer utilizing a pair of cams with a corresponding pair of movable switch members.
In U.S. Pat. No. 3,575,561 of Robert L. Wooding, a switch control is shown having a pair of cams for operating a snap-action switch. The device further includes a pair of movable levers one of which is interconnected to the switch blade, both levers being continuously urged toward operative engagement with the cam means. The levers are selectively moved by the cam means to provide the desired control.
In U.S. Pat. No. 3,648,476 of applicant, which patent is owned by the assignee hereof, a control utilizing a bimetal switch for controlling the drive motor of the ice maker is shown.
John L. Harris, in U.S. Pat. No. 3,699,281, shows a switch control wherein a latch prevents closure of the contacts until a timer knob has been turned far enough to ensure complete closure of the contacts. The latch allows the contacts to assume very close proximity before releasing to avoid contact bounce. The control utilizes a pair of followers and a pair of cams so as to provide the desired rapid closing of the single throw switch.
In U.S. Pat. No. 3,710,043 of Wallace L. Linn, et al., a switch is provided with electrical contacts carried by cooperating switch blades intermittently engaged with one another in response to intermittent release of energy generated by rotating resilient means. A finger operating the switch is deflected by a ramp on the cam so as to flip the switch contacts when the finger rides past the ramp. The switch comprises a single throw switch with the control causing accurate rapid closing thereof under the timed control of the driven spring finger.